Network Audio Players/Servers

Auralic's Aries G2.1 is not only a network-attached music storage device but, like the recent Grimm Audio MU1 [HFN Dec '20], Innuos Statement [HFN Jan '20], Melco N10 [HFN Jun '19] and Roon Nucleus+ [HFN May '18] it also includes proprietary signal conditioning. In this case the 'conditioning' – upsampling and/or downsampling to 2x or 4x the base 44.1kHz/48kHz sample rates to a maximum of 192kHz – is offered over a choice of four digital filter types. 'Precise' is a very long-tap, linear phase FIR filter that offers the flattest responses (+0.05dB/20kHz) and most complete stopband rejection (up to 133dB) at the expense of extended pre/post 'echoes' in the time domain [see black traces, Graph 1 below]. Another linear phase filter, with fewer taps, is called 'Dynamic' and offers a similar 133dB stopband rejection and flat response, with minor ±0.002dB ripples, and reduced pre/post echoes [red traces, Graph 1]. The 'Balance' filter option trades a still acceptable 70dB stopband rejection for a slightly earlier in-band roll-off (±0.0dB/18kHz to –2.2dB/20kHz) and much reduced ringing and group delay in the time domain [blue traces, Graph 1]. The only minimum phase filter, 'Smooth', has no acausal echoes (no pre-ripples, but significant post-event ripples) combined with a 67dB stopband rejection and almost identical HF roll-off to the 'Balance' option [green traces, Graph 2].

Jitter, tested with three AES/USB DACs, is unaffected by the digital filter and is essentially defined by the choice of hardware. Similarly, the dCS Vivaldi One [HFN Feb '18], Mola Mola Tambaqui [HFN Nov '19] and Mytek Brooklyn [HFN Aug '17] showed no significant difference in either distortion or A-wtd S/N via either USB, S/PDIF or AES streams – remaining at 0.00005-0.00007% (0dBFs to –30dBFs) and 118.5dB, respectively, for the Tambaqui. Jitter remained <10pec via all digital interconnects via the Mytek and Tambaqui DACs [see Graph 2, below]. PM